As someone who used to work for QF, doing this sort of job, I did this all the time, particularly if a flight was oversold. Once an inbound flights ETA would have failed to meet the MCT, all connecting pax were offloaded and rebooked, and those who were waitlisted were confirmed.
*IF* there were still seats left, then those on the delayed inbound might be put back onto the original flight, in order of presentation (rather than FF status), but it is a fairly standard practice with most airlines (not with EU airlines, though, due to EU261).
Dave